1,721,080 research outputs found
Microhabitat patterns of soft-bodied benthic algae in a lowland river largely fed by groundwater
No full textIn lowland rivers largely fed by groundwater, the aquifer resurgence plays a major role in supporting local plant diversity. However, large knowledge gaps exist with regard the role of groundwater on algal diversity and spatial arrangement. In this context, our main aim was to evaluate the distributive gradients of soft-bodied benthic algae across a mid-size lowland river with a bottom dominated by hard substrate (Oglio River, north Italy). Along the investigated river sector, a clear segregation both for taxa and for environmental data was observed, especially in terms of pH, hydrological variables and nutrient availability. Overall, we recorded an important contribution of groundwater supply in shaping the structure and complexity of algal communities at the microhabitat level (in the meter range) during the river base flow. All these considerations shed new light on the response of algal taxa to a relevant groundwater ingression in a lowland river
Fragmentation and groundwater supply as major drivers of algal and plant diversity and relative cover dynamics along a highly modified lowland river
No full textAlgae and aquatic vascular plants were investigated along a highly modified medium-sized lowland river (Oglio River, northern Italy). We focused on the role of fragmentation and groundwater supply in driving macrophyte assemblages, paying particular attention to soft-bodied benthic algae. Four different a priori stretch types (dammed, groundwater-dependent, potamal and rhithral) were identified along the river longitudinal gradient as proxies of river hydrology and relative human-induced flow alterations. Over three years (2009–2011), taxa diversity, cover data, spatial and temporal dynamics and indicator and detector species were compared with physical, chemical and hydrological variables at 30 different river sites. Data was explored by indicator species analysis, nonmetric multidimensional scaling, and PROTEST. A total of 88 taxa, of which 36 were algae (equal to 40.9% of the total diversity), 3 bryophytes (3.4%) and 49 vascular plants (55.7%), were recorded. Taxa diversity peaked at the groundwater-dependent sites for both algae and vascular plants (with a mean of 12.8 ± 2.7 and 12.7 ± 4.8 taxa per site, respectively). Algae cover values were one order of magnitude higher than those of vascular plants (with an overall mean of 37.0 ± 24.2% per site). The vascular plants counterbalanced the algae coverage values exclusively at the dammed sites (27.6 ± 23.2% vs 28.2 ± 13.9%, respectively). A clear zonation of communities emerged from the multivariate analysis, which revealed taxa rearrangements that largely overlapped the river stretch types. Inter-annual comparisons confirmed the strong stability of the primary producer communities in the short term (three years). Our work substantiates the pivotal role played by fragmentation and hydrology, in addition to groundwater, in structuring riverine macrophyte communities. Further investigations are needed to resolve the uncertainty surrounding the non-linear responses of macrophytes to the physical and chemical conditions of rivers
Species and functional plant diversity in a heavily impacted riverscape: implication for threatened hydro-hygrophylous flora conservation
No full textWetlands play a central role in sustaining biodiversity, especially in landscapes altered by human activities. In overexploited floodplains, alteration of river hydro-morphology has resulted in the progressive disappearance of riparian wetlands. Consequently, several native hydro-hygrophilous plants have experienced a dramatic decline. In this context, artificial shallow water bodies, actively managed for agricultural purposes, could act as potential refuge for relict biodiversity. However, their role in plant conservation has been at present scarcely investigated. In this framework, a floristic study was performed to clarify the patterns of species and functional plant diversity with respect to the origin, hydrology and structural complexity of 60 marginal habitats within the watershed of the Oglio River (3800 km2, Northern Italy). The basin of this regulated river is heavily exploited by intensive agriculture and farming, occurring over 75% of the surface; wetland habitats occupy small surfaces, generally of a few hectares, and are scattered in the territory. The sampled plants were classified by life-growth form and were grouped into four clusters representing the main hydro-hygrophilous functional zones of investigated habitats. An appreciable regional diversity (208 taxa) was found. The typical floristic contingent was composed by lemnids, large helophytes and semihygrophilous opportunist species. Experimental data revealed: (i) the predominance of terrestrial species within shallow aquatic habitats of the Oglio riverscape and (ii) the deterioration of the obligate aquatic plant contingent and the helophyte representativeness in riparian zones. Overall, plant diversity appears to be driven more by the sites origin (natural vs. artificial) and their structural complexity rather than by
their hydrological features (lentic vs. lotic). On the other hand, the present data confirm the important role of the artificial drainage system as temporary valuable habitat for lowland macrophytes
Relazione tra il ciclo stagionale di Trapa natans L. e la qualità dell’acqua nella Lanca di Po (Villanova d’Arda, Piacenza).
No full textComposizione e struttura delle comunità vegetali bentoniche in sistemi lacustri soggetti a regolazione artificiale del livello idrometrico
No full textA remote sensing approach to monitor the conservation status of lacustrine Phragmites australis beds
No full textEditorial: Multiple Roles of Alien Plants in Aquatic Ecosystems: From Processes to Modelling
No full textInvasive alien species are one of the most significant contemporary challenges threating biodiversity, ecosystem functioning, and human wellbeing (Rai and Singh, 2020), resulting in major economic and environmental damages and losses (Pimentel et al., 2005). Biological invasions are favored by
ecosystems’ over-exploitation and climate change, and the progressive accumulation of invasive species strongly weakens the invaded communities by occupying empty phylogenetic and functional spaces or by excluding natives (Dalle Fratte et al., 2019). Among ecosystems, freshwaters seem to be
particularly prone to invasions due to their high natural dynamism associated with a global hydrological and trophic alteration due to human activities (Dudgeon, 2019). This urgently calls for a better understanding of the multiple roles played by invasive aquatic alien plants (IAAPs). To this regard, the present Research Topic offers novel perspectives on IAAPs science and on the implications of their establishment
Role of ephemeral vegetation of emerging river bottoms in modulating CO2 exchanges across a temperate large lowland river stretch
No full textRivers and marginal wetlands contribute significantly to the carbon (C) exchange rate per unit area compared to adjacent terrestrial ecosystems, due to high C inputs, metabolic activity and CO2 supersaturation. Within riverscapes, the contribution of emerging bottoms (i.e. parafluvial zones) and ephemeral vegetation (i.e. microphytobenthos or annual vascular plant communities) to the C metabolism is understudied. The aim of this study was to evaluate the CO2 exchange rates at the water- and emergent sand bar-atmosphere interfaces within a lowland large temperate river stretch. CO2 fluxes were measured seasonally, in summer (August 2007) and winter (March 2008) via static closed chambers, together with the primary producers’ biomass (microphytobenthos and vascular macrophytes). Our results showed that the river was a CO2 source (between 0.2 and 7.6 mmol CO2 m−2 day−1), whilst the vegetated parafluvial zones acted as a net sink, with assimilation rates peaking at 623.4 mmol CO2 m−2 day−1. Emerging bare sediments were on the contrary net emitting CO2 systems (2.7–60.1 mmol CO2 m−2 day−1). Within lotic environments, seasonally emergent vegetated sand bars may represent important C fixation hot spots, with summer primary production particularly contributing to offsetting CO2 emissions and counterbalancing the heterotrophic metabolism of the saturated zones. Based on these outcomes, we suggest that studies addressing the strictly aquatic fluvial environment, which is generally a CO2 emitter, should be linked to those from transitional areas in order to better integrate terrestrial and aquatic C budgets
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